Noisy Hot Water - Expansion pipe drawing in water

[Tesla]

OK John, the Baxi manual does state either arrangement as suitable though.

The cold feed wasn't blocked, I was able to rod it quite easily, bit of black on the end of the rod but that's all.

If the boiler was full of sludge/dirt, what symptoms would you expect to see?
If flow through the boiler was poor would the pump then draw from the vent, even on speed 1?

The system is 12-13 years old at a guess which is why I question if I need to move the feed and or vent. It would of always been like this if that were the case?

Hope you don't feel I am questioning you, just trying to get the workings clear in my mind.

Also, I'm pretty sure it didn't have any inhibitor in for a number of years (I've since rectified and replaced all the rads)

 

[JohnD]

The Vent and the F&E pipes connections are supposed to be on the same pipe, close together, to prevent a pressure differential between them

Are you sure the manual doesn't say they can (both) be on the flow or (both) on the return?

It is the pressure differential that is causing the sucking. The air will have accelerated internal corrosion, even if it had started out with inhibitor.

sludge would normally manifest with black at the bottom of the rads when you take one off. It also restricts circulation and wears out the pump. Limescale is usually inside the boiler and difficult to see or remove, it makes the boiler "sing" like a kettle coming to the boil, or bonk and bang. However Sentinel now do X200 which you put in and leave in, with the inhibitor, and the limescale slowly washes away.

When you have done all your changes, I would certainly give it a clean with X400. If the circulating water goes jet black, you'll know there was old sludge that is being washed away (you have to drain and rinse it all out after 4 weeks and use inhibitor in your final fill)

 

[Tesla]

Hi John,

I'll scan in the manual page and post it up.

When bleeding the rads I get black water coming out with small deposits, easy to see if I bleed some water out into a white plastic tray.

Thanks again for your advice.

 

[Tesla]

Morning,

I dosed the system with 1L of X400 yesterday evening.

It's still early days so I am not jumping to conclusions but the heating was definitely quieter this morning.
The frequency of whooshing noises is less and when it does occur it's only very briefly.

Hopefully the chemicals are breaking some sort of blockage/restriction up.

I've no idea what the waterways on the inside of my boiler are like? Obviously it has a 22mm flow and return but what does the water flow around/in inside the boiler?

 

[JohnD]

If it's an old Baxi Backboiler I presume it will be cast iron.

I looked inside my old cast iron boiler after it was removed, and it would have been very hard to remove the scale and rust without an acid cleaner (which in fact I had used a year before but there was a lot left)

I don't think X200 was around at the time.

I would have wanted a system filter as well to catch the loosened particles.

 

[Tesla]

Hi John,

Was hoping something like that wouldn't be posted. Will see what happens, if anything with the X400 over the next few weeks.

How feasible is it that a 22mm pipe could be partially blocked? Unheard of?

 

[JohnD]

the blockage is most usually in the 15mm pipe at the point where it Tees onto the circulating pipe. It may be a combination of black iron oxide mixed with limescale, the limescale makes it hard. Pure black sludge will be softened by the X400.

You can detect the presence of a black sludge accumulation in a copper pipe with a magnet, which will be attracted to the sludge.

 

[Tesla]

the blockage is most usually in the 15mm pipe at the point where it Tees onto the circulating pipe. It may be a combination of black iron oxide mixed with limescale, the limescale makes it hard. Pure black sludge will be softened by the X400.l

Cheers John, I cut into the 15mm feed and rodded down through the elbow. It wasn't blocked but my electricians cable rod turned from yellow to black, the inside of the pipe work is all black.

 

[Tesla]

Hello again,

I am now doubting whether the air is entering through the vent.

There is no question that the vent initially sucks a bit when the pump first kicks in, however it may not suck out all of the water in the vent pipe. I've been told a little bit of an initial suck is normal.

The reason for my doubt is that I placed a balloon over the vent pipe, happened to have a box of party stuff in the attic, seemed sensible (as long as the balloon didn't disappear down the vent!). I inflated the balloon a bit, about the size of a cricket ball and with it placed over the vent it deflated then inflated slightly, looked like a slow-beating heart.

The whooshing noise occurred but the balloon's behaviour was the same.

If I turn up the pump speed, the frequency of the whooshing occurring increases.

The whooshing is definitely air through the pump as 10 seconds later it starts bubbling into the rads. I can bleed the upstairs rads daily for 5-10 seconds.

So, question is, where else could this amount of air be getting in?

The drain point I thought so I turned off the radiator next to it but made no difference. I guess I could turn each rad off one-by-one to easily eliminate those? If it whooshes on hot water only then it can only be something on the boiler?

 

[JohnD]

it might be sucking air through a joint on the suction side of the pump. air will get through a smaller gap than water, so there might or might not be a water and scale mark at the leak.